Every time I go to either Petco or Petsmart I bring my cat Marley with me.
He is a crowd pleaser since he is a Munchkin cat (midget cat).
So I just put his harness on and a leash, set him in the cart with the stuff and we just walk around and he smells things or sees the fish, etc. Its a good outing. Lol.
It is a plus though to have your kitty leash trained as I do mine, since he was 8weeks old.

I have seen other pets/furry kids but i have never brought one in' I have thought about bringing our ferrets in for a picking of another but' I to have wondered how much the excitement will be'' you will never though unless you try =)

I've also brought my cat to petco for vaccinations. They do have a line for vaccinations but you're often in between people with dogs. If you want to bring your cat in during this time wait until there isn't a line to bring your cat in or wait and leave someone with your cat in the car and call them to bring the cat in when its your turn.

I've been in the store when the vets are there to offer vaccines. The staff creates separate lines to decrease interactions. It is a lot of stimulation, but if you call in advance (grooming), they can tell you a good time to bring you pet in.